Chemodiversity and biological activity of the genus Alpinia (Zingiberaceae)
Several species of the large and taxonomically complex genus Alpinia are of ethnobotanical importance in (sub)-tropical regions of Asia and Oceania. Different parts of the plants (rhizomes, leaves, fruits) are used mainly for medicinal purposes, as food additives and spices (e.g. A. officinarum Hance, A. galanga Willd., and A. oxyphylla Miq.). Current comparative studies on the chemical profiles of rhizomes of 25 Alpinia species revealed the presence of labdane diterpenes, acetylated phenylpropenes, kavalactones, specific flavonoids, and diarylheptanoids, each being derived from distinct genetically defined pathways. Phytochemical methods applied include various chromatographic techniques for profiling (HPLC-UV/Vis, TLC) and isolation (CC, MPLC, pTLC), and spectroscopic methods (NMR, MS) for structure elucidation of obtained compounds. Methanolic extracts and purified compounds were routinely checked for bioactivity, against the phytopathogenic fungus Cladosporium sphaerospermum and the pest insect Spodoptera littoralis. In addition, some of the pure compounds isolated were studied for their anti-angiogenic properties in a zebrafish model system. The labdane-diterpene zerumin A dose-dependently inhibited vessel formation on both wild type and Tg(fli1a:EGFP)y1 zebrafish embryos through effects on multiple molecular targets related to angiogenesis. The occurrence of different secondary metabolites within rhizomes of Alpinia is presented, and bioactivity results are discussed.